Both of these sentences will be understood, and generally can mean the same thing.
The potential difference between the two, is that the first (present tense) can potentially focus on the future actions that the person can take - and will be more common when assuming good-faith of the other person.
If you want to do X, [you can do] Y
Is a simple statement that in order to achieve the outcome they want, there is a course of action they should take. Your tone of voice can of course imply that they should have done this, but it's not necessarily implied by the word choice.
However, using the past tense gives much more emphasis on the idea that they should have already done these things, if that was actually their goal.
If you wanted to do X, [you should have done] Y
Again, the tone of voice will make it clear whether you are critisizing somebody or not - so it is possible to use this phrase in a well meaning way.
However, the default implication is that you feel somebody should have taken the action if they truly wanted to achieve the goal. That is, you're critisizing their lack of action, and possibly questioning their true commitment to the goal.
As mentioned, the tone of the conversation will override the implications of either sentence - but they are there and can add additional emphasis to what you're saying.